向现有的电子邮件文件添加附件

Question

我有一个现有的电子邮件文件，其中包含正文和附件。

我只是想给这个文件添加附件，而不是删除现有的附件。

我用下面的代码创建eml:

public static void createMessage(String to, String from, String subject, String body, List<File> attachments) {
try {
    Message message = new MimeMessage(Session.getInstance(System.getProperties()));
    message.setFrom(new InternetAddress(from));
    message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
    message.setSubject(subject);
    // create the message part 
    MimeBodyPart content = new MimeBodyPart();
    // fill message
    content.setText(body);
    Multipart multipart = new MimeMultipart();
    multipart.addBodyPart(content);
    // add attachments
    for(File file : attachments) {
        MimeBodyPart attachment = new MimeBodyPart();
        DataSource source = new FileDataSource(file);
        attachment.setDataHandler(new DataHandler(source));
        attachment.setFileName(file.getName());
        multipart.addBodyPart(attachment);
    }
    // integration
    message.setContent(multipart);
    // store file
    message.writeTo(new FileOutputStream(new File("c:/mail.eml")));
} catch (MessagingException ex) {
    Logger.getLogger(Mailkit.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
    Logger.getLogger(Mailkit.class.getName()).log(Level.SEVERE, null, ex);
}

}

但是我如何添加到现有的，而不是创建?

Answer 1

public static void addAttachment(Message msg, File attachment) throws Exception {
    //Create the new body part and add the file
    MimeBodyPart attachment = new MimeBodyPart();
    DataSource source = new FileDataSource(file);
    attachment.setDataHandler(new DataHandler(source));
    attachment.setFileName(file.getName());
    //Add the new body part to the e-mail
    msg.getContent().addBodyPart(attachment);
}

在上面的方法中，使用附件创建了一个新的bodypart，然后将该bodypart添加到已经存在的电子邮件的multipart中。